Abstract 060: CCN1/a6β1 Mediates Myocardial Injuries Induced by Work Overload or by Doxorubicin in Mice
Introduction: Matricellular protein CCN1 is expressed in myocardial infarction, pressure overload, and ischemia in mice, and in patients with a failing heart. Despite its well-documented angiogenic activities, CCN1 promotes fibroblast apoptosis in some contexts. The role of CCN1 in an injured heart was not clear. We assessed the hypothesis that CCN1 plays a detrimental role and mediates cardiac injury through its proapoptotic activities.
Methods and Results: To test the role of CCN1 in cardiac injury, we employed two different myocardial injury models in mice, including a work-overload-induced injury created by isoproterenol treatment (ISO; 100 mg/kg/day; s.c. for 5 days; n= 6 for each group) and an injury induced by the cardiotoxicity of doxorubicin (DOX, single dose of 15 mg/kg; i.p. sacrificed after 14 days). Ccn1 expression was induced in the damaged myocardium in both injury models. A line of knock-in mice carrying an apoptosis-defective Ccn1 mutant allele, Ccn1-dm, which has disrupted integrin α6β1 binding sites, were tested in the ISO- or DOX -induced cardiac injury. Myocardial damage was seen in tissues from wile-type (WT) hearts after receiving ISO. Ccn1dm/dm (DM) mice possessed remarkable resistance against ISO or DOX treatments and exhibited no tissue damage or fibrosis compared to WT mice after H&E or Masson’s trichrome stainings. DM mice were resistant to both ISO- and DOX-induced cardiac cell apoptosis, indicating that CCN1 is critically mediating cardiomyocyte apoptotic death in cardiac injury. Moreover, we found that death factor Fas ligand (FasL) and its receptor Fas were upregulated in WT mice receiving ISO or DOX treatments by immunohistochemical staining, compared with the PBS-control. 8-OHdG-positive, a marker for oxidative stress, cardiomyocytes were increased by ISO or DOX treatments as well. In contrast, the expression of Fas/FasL, and the 8-OHdG-positive cardiomyocytes in the myocardium of DM mice were not changed by ISO or DOX.
Conclusions: We identify CCN1 as a novel pathophysiological regulator of cardiomyocyte apoptosis in cardiac injury. Blocking apoptotic function of CCN1 effectively prevents myocardial injury in mice. CCN1 and its receptor α6β1 represent promising future therapeutic targets in cardiac injury.
- © 2013 by American Heart Association, Inc.